Method and apparatus for washing items having cloth with microwaves

ABSTRACT

The present invention pertains to an apparatus for cleaning items having cloth. The apparatus comprises a housing having a microwave cavity. The apparatus comprises a drum disposed within the cavity which is made of a material which is transparent to microwaves. The items are disposed in the drum when they are cleaned. The apparatus also comprises a microwave source in communication with the cavity to provide microwave energy to the cavity. Additionally, the apparatus comprises a fluid source in contact with the cavity to provide fluid to the cavity. The apparatus comprises a mechanism for moving the drum. The mechanism is connected with the drum. The present invention pertains to a method for washing items having cloth. The method comprises the steps of placing the items having cloth into a washing machine. Next, there is the step of irradiating the items with microwaves to clean the items. Preferably, after the placing step, there is a step of agitating mechanically the items in the washing machine. Before the agitating step, there is preferably a step of adding liquid to the washing machine so the items are made wet by the liquid. Before the agitating step, there is preferably a step of placing detergent into the washing machine so the items are contacted by the detergent.

FIELD OF THE INVENTION

[0001] The invention relates to the use of microwave energy for the processes of washing and drying. Although this invention addresses the washing and drying of laundry clothes and fabrics, it certainly includes cleaning processes in all industrial applications. Examples of such industrial applications include hosiery, rugs, textiles, and other objects that may not allow the use of acids and other strong chemicals.

[0002] It relates to a process where microwave energy is radiated on the items to be washed with water and detergent. The mechanical agitation provided by washing machines may be maintained but equivalent or better washing results (than conventional machines) may still be obtained without extensive agitation. It may not be necessary to use hot water, as with conventional washing machines, because the water will be heated during the microwave exposure. The actual contribution of microwave energy comes from the ability of microwaves to rotate the polar water molecules everywhere, i.e., within the fibers (of the fabric), the surface of the fiber, and the surface of the fabric. Wherever the water and detergent molecules can reach, microwave energy can agitate the water molecules, providing micro-agitation to remove dirt or oil at sites inaccessible by other methods. The remaining steps of rinsing and spinning for centrifuge drying could then be carried out by state-of-the-art techniques being used routinely in most washing machines.

[0003] It further relates to the integration of the state-of-the-art washers, dryers and microwave ovens into one system. Microwave energy has been used for drying of various ceramics where substantial savings in time and energy has been obtained. It is particularly beneficial for thicker objects—in this specific case thicker fabrics—where microwave energy will preferentially heat the moisture in the fabric and drive it out more rapidly than an external heating source.

BACKGROUND OF THE INVENTION

[0004] The use of microwave energy in the food industry and the domestic microwave oven have been the dominant applications for thermal processes. The broad acceptance of the use of microwave energy in this particular area appears to result from the consistent and reproducible heating of all food, because of the universal presence of an excellent microwave absorber—water. FIG. 1 illustrates the behavior of a polar water molecule in the 2.45 GHz microwave field. Water molecules are polar (FIG. 1a) and readily respond to the microwaves by lining up with the field (FIG. 1b), in a manner similar to iron filings in a magnetic field. The alternating nature of microwave energy makes the polar water molecules change their orientation with the field (FIG. 1c), thereby setting the molecules into rotational motion. This rapid movement of the molecules adds kinetic energy which results in heating of the water.

[0005] The process of washing consists mainly of detergent action on the dirt in the fabric, which is usually assisted by the mechanical agitation provided by all washing machines. Generally, a detergent consists of compounds having a stearate ion, such as sodium stearate or sodium lauryl sulfate. Each molecule has both a hydrophobic and a hydrophilic end. For example, the stearate ion has a long nonpolar hydrocarbon end that is hydrophobic and a carboxyl group (COO—) that is hydrophilic. With soap molecules dispersed in water, the cleaning action occurs because the hydrophobic (hydrocarbon) end gathers around the oil, dirt or grease pointing inwards to the oil and away from water, while the hydrophilic end (carboxyl groups) remains on the outside facing the surrounding water. The aggregate so formed, called a micelle, can then be washed away in the water. This is schematically illustrated in FIG. 2. FIG. 2a shows the oily dirt spot on the fabric. When soap is added to the water the hydrophobic end of the soap molecule attaches itself to the dirt as indicated in FIG. 2b. On agitation the dirt is trapped within the soap micelle, which is now dispersed in water as shown in FIG. 2c, and can be easily washed away.

[0006] It is worth mentioning here that agitation is necessary in order to form soap micelles which will contain the oil or dirt. To illustrate this situation, consider some vegetable oil added to water. The oil will float on the water. If some soap is added and the liquid is shaken well, only then will the oil disperse in soap micelles throughout the water. The same result occurs when oil is within a fabric. If dirt is deep within a thick fabric, rigorous agitation will be desirable at that site to remove it effectively.

[0007] It has been mentioned above that microwave energy rotates the polar water molecule, thereby heating the water, and making microwave ovens very useful for heating food. For microwave washing, on the other hand, although heating is desirable, the major advantage is the agitation of the water molecule, which, in the presence of soap, provides the means to effectively remove dirt from any site, including those deep within the fiber of the fabric.

[0008] The major characteristics of microwave energy include the rapid and internal heating, which has attracted researchers to use microwave energy for innovative materials processing. The use of microwave energy to process a variety of ceramic, polymeric and composite materials offers many exciting opportunities. Although microwave processing is well established in the food, rubber, textile and wood industries, it is still under development for processing inorganic and other organic materials, chemicals and certain minerals [Sutton, MRS Bulletin, p. 22, Vol. XVIII, No. 11, 1993].

[0009] Microwave heating is fundamentally different from heating with most other sources, which generally provide heat to the surface of the material, either by radiation or convection. Heat then penetrates the material through thermal conduction. On the other hand, microwave energy penetrates the bulk of the material, and simultaneously heats the material volumetrically through dielectric loss. In this way, microwave energy provides rapid heating rates that allow savings in time and energy. Researchers have by now recognized from various applications of microwaves to materials processing that this technology provides a powerful new energy source and processing tool. Besides the savings in energy and cost (due to the rapid processing cycle), the greatest advantage of the novel internal heating pattern is the unique microstructure and mechanical properties of the material, which cannot be achieved using external heating sources.

[0010] The increasing awareness of the potential of microwave processing of materials has led to extensive research and development efforts worldwide to explore and utilize this potential. The Materials Research Society (MRS) held the first international symposium on microwave processing of materials in 1988 [Microwave Processing of Materials I, MRS Proc., Vol. 124, (1988)]. Since then, MRS and the American Ceramic Society have sponsored symposia on this topic on alternating years [Microwave Processing of Materials II, III, IV & V (In press, 1996), MRS Proc., Vol. 189 (1991), Vol. 269 (1992), Vol. 347 (1994); Microwave: Theory and Applications in Materials Processing I & II, Am. Ceram. Soc., Ceram. Trans. Vol. 21 (1991), Vol. 36 (1993), Vol. 59 (1995)]. Other societies have also held special symposia on microwave processing of polymers [Proc., Am. Chem. Soc., Vol. 66 1992] and microwave chemistry [1st World Congress on Microwave Chemistry, Intl. Microwave Power Institute, Breukelen, The Netherlands (Sep. 3-5, 1992)]. The International Microwave Power Institute holds meetings every year on microwave power technology, which includes papers on microwave thermal-processing.

[0011] Due to the poor thermal conductivity of polymeric materials and composites, microwave processing has enjoyed growing interest over the conventional or infrared methods, because it provides rapid and relatively uniform heating of even large volumes. In processing of polymer composites, increased reaction rates and a greater extent of cure have been reported in microwave cured samples, as compared to conventionally cured samples. The effect of microwave radiation on the curing of thermosetting polymers was reported to be a function of the dipole moments of the monomer and the curing agent. Microwave energy has also been used for the pyrolysis of metalorganic precursor compounds for powder synthesis [Willer-Porada, MRS Bulletin, p. 51, Vol. XVIII, No. 11, 1993]. Generally, an acceleration in the reaction rates is reported. A number of reports show no effect, whereas in certain cases the reaction rates have been retarded. Although enhancement in reaction rates is dominant in most cases, careful analysis of materials properties and experimental data is required to fully exploit the technological benefits of microwave processing. Observations so far indicate that slower reactions tend to show a greater effect under microwave irradiation than faster reacting systems, and that the magnitude of the so-called microwave effect decreases as the temperature of reaction increases, perhaps because at higher temperatures the reaction rates are already faster [Lewis and Shaw, MRS Bulletin, p. 37, Vol. XVIII, No. 11, 1993].

SUMMARY OF THE INVENTION

[0012] A method and apparatus is disclosed for improving the efficiency and quality of washing of laundry fabrics, using microwave energy during the washing cycle. The presence of microwaves rotates the polar water molecules, at all sites on the fabric and within the fiber of the fabric during the washing cycle, thereby enhancing the cleansing action. The same source of microwave energy, combined with air flow, can be used for the drying process. Most of the functions used in state-of-the-art commercial washers and dryers, such as the washing, rinsing, spinning and drying cycles, can be integrated into a single system, together with the microwave source used in the state-of-the-art kitchen/commercial microwave ovens.

[0013] The present invention pertains to an apparatus for cleaning items having cloth. The apparatus comprises a housing having a microwave cavity. The apparatus comprises a drum disposed within the cavity-which is made of a material which is transparent to microwaves. The items are disposed in the drum where they are cleaned. The apparatus also comprises a microwave source in communication with the cavity to provide microwave energy to the cavity. Additionally, the apparatus comprises a fluid source connected to the cavity to provide fluid in the cavity. The apparatus comprises a mechanism for moving the drum. The mechanism is connected with the drum.

[0014] The present invention pertains to a method for washing items having cloth. The method comprises the steps of placing the items having cloth into a washing machine. Next, there is the step of irradiating the items with microwaves to clean the items. Preferably, after the placing step, there is a step of agitating mechanically the items in the washing machine. Before the agitating step, there is preferably a step of adding liquid to the washing machine so the items are made wet by the liquid. Before the agitating step, there is preferably a step of placing detergent into the washing machine so the items are contacted by the detergent.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the accompanying drawings, the preferred embodiment of the invention and preferred methods of practicing the invention are illustrated in which:

[0016]FIG. 1 shows a polar water molecule (1 a) and its orientation in presence of a 2.45 GHz microwave field (1 b). In the alternating field the reorientation of the polar molecule results in rotation of the water molecule (1 c).

[0017]FIG. 2 illustrates the cleansing action of soap. The oily dirt spot on the fabric is shown in FIG. 2a. With the addition of soap, the hydrophobic ends of the soap molecules gather around oily dirt spot (2 b). On agitation the hydrophobic ends completely surround the oil. The other ends of the soap molecules, being hydrophilic, keep the micelle so formed in water (2 c), which is eventually washed away.

[0018]FIG. 3 depicts a schematic for the process and apparatus for the integrated microwave washing and drying system.

[0019]FIG. 4 shows two test towels with various strong stains before washing. The stains are described in FIG. 5. C & M stand for (to be washed by) Conventional and Microwave methods respectively.

[0020]FIG. 5 briefly describes the stains intentionally put on the towels, which were washed with and without microwave exposure.

[0021]FIG. 6 shows the towels after washing by conventional and microwave techniques. Stains on the towel washed during microwave exposure are clearly much lighter than those on its counterpart washed in a conventional washing machine.

[0022]FIG. 7 compares the towels washed by conventional and microwave techniques. The background (not the stains) on the towel washed by microwaves was brighter than that from the conventional washing (as if it had been bleached). The contrast is visible between the arrows on the photograph. The band with M written on it is brighter than the band with C written on it, which has a relatively yellowish tint.

[0023]FIG. 8 shows microscopic photographs of the amount of grease present in the towels after washing. The photos show that a larger amount of grease is still present in the towel washed by conventional means than in the one washed with microwave energy.

[0024]FIG. 9 shows microscopic photographs of the extent of cleaning of engine oil by both techniques. Conventional cleaning between the fibers of the fabric is clearly not as good as that with microwave washing.

[0025]FIG. 10 similarly shows the enhanced cleaning by microwave energy of the oil wood stain deep into the fibers.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] Referring now to the drawings wherein like reference numerals refer to similar or identical parts throughout the several views, and more specifically to FIG. 3 thereof, there is shown an apparatus 100 for cleaning items having cloth. The apparatus 100 comprises a housing 10 having a microwave cavity 12. The apparatus 100 comprises a drum 16 disposed within the cavity 12 which is made of a material which is transparent to microwaves. The items are disposed in the drum 16 when they are cleaned. The apparatus 100 also comprises a microwave source 14 in communication with the cavity 12 to provide microwave energy to the cavity 12. Additionally, the apparatus 100 comprises a fluid source 18 in contact with the cavity 12 to provide fluid to the cavity 12. The apparatus 100 comprises a mechanism 22 for moving the drum 16. The mechanism is connected with the drum 16. Preferably, the apparatus 100 also comprises a mechanism 24 for releasing fluid from the cavity 12. The releasing mechanism 24 is connected with the cavity 12.

[0027] The present invention pertains to a method for washing items having cloth. The method comprises the steps of placing the items having cloth into a washing machine 100. Next, there is the step of irradiating the items with microwaves to clean the items. Preferably, after the placing step, there is a step of agitating mechanically the items in the washing machine 100. Before the agitating step, there is preferably a step of adding liquid to the washing machine 100 so the items are made wet by the liquid. Before the agitating step, there is preferably a step of placing detergent into the washing machine 100 so the items are contacted by the detergent.

[0028] Preferably, the irradiating step includes a step of irradiating the items with microwaves at a 2.45 GHZ or other frequencies. The adding step preferably includes a step of adding approximately 3 gallons (or less) of water to one cubic feet of uncompressed dry laundry load during the washing cycle. Preferably, after the irradiating step, there is a step of drying the items with microwave energy.

[0029] In the operation of the preferred embodiment, this invention presents the process and apparatus that utilizes microwave energy to produce enhanced cleaning action during washing, similar to the enhancement in reactions mentioned above in microwave processing of materials. The apparatus may be designed such that, combining the power source in microwave ovens and state-of-the-art techniques used presently in conventional washers and dryers, the two processes of washing and drying can be integrated into a single system. In this integrated system, microwave energy will assist in improving the process and hence quality of washing. In the drying process, since microwave energy will selectively and rapidly heat the moisture and drive it out of the fabric, it will enhance the drying cycle as well.

[0030] The present invention exploits the advantage of microwave energy combined with the detergent action for improving the efficiency and quality of washing. As outlined above, oil will generally float on water. The addition of a detergent, combined with shaking well, disperses the oil in soap micelles throughout the water. Shaking provides the oil and the detergent molecules an opportunity to arrange in the form of micelles dispersed in water. It has been observed under microscopic examination that the dirt, oil or grease stains are soaked into the fiber of the fabric. In this case, the deeper the mechanical agitation, the better the cleaning of the fabric. The mechanical agitation produced by most of the state-of-the-art commercial washing machines simply stirs the soapy water, which may only effectively clean the surface, while providing little or no agitation within the fibers of the fabric to provide deeper cleaning. The result is that this incomplete cleaning of white clothes gives them an off-white appearance, which has to be removed with some other chemical agent stronger than soap, generally a bleach.

[0031] Since microwave energy penetrates the fabrics, it produces rotational motion of the water molecules at all sites, from the surface of the fabric to deeper sites within the fibers of the fabric. With the use of microwaves, it is possible to provide the micro-agitation at any place where water and soap molecules can penetrate, which obviously could be as small as the molecules itself. Thus the use of microwave energy provides the cleaning capability that no other washing machine can provide. Another advantage of the use of microwave energy is the heating of the water. Most washing machines use hot water to improve the washing process. Microwave washers can use cold water and heat it during the process of washing.

[0032]FIG. 3 schematically depicts an apparatus 100 for the integrated microwave washer and dryer. The loading into the apparatus 100 could be from the front like most state-of-the-art commercial dryers. The apparatus 100 consists of a metallic microwave cavity 12 having a screened door to allow visual observation while preventing microwave exposure, similar to the doors on state-of-the-art microwave ovens used in most kitchens. The door is also water-tight like some state-of-the-art front-loading washers. Microwaves are generated (at 2.45 GHz) from a microwave source 14, similar to state-of-the-art microwave ovens, and then fed into the cavity 12 through the port 18 indicated in FIG. 3. Microwaves penetrate different lengths into different materials, depending on the dielectric properties of any particular material. A variety of microwave-transparent materials are being widely used for microwave cookware. The drum 16 indicated in the FIG. 3 is made of such a state-of-the-art microwave-transparent unbreakable polymeric material. This drum 16 preferably contains holes similar to those used in most state-of-the-art commercial dryers. Thus, essentially a standard dryer design is used, but the drum is made of microwave-transparent material, and in the housing of the dryer, at the stop, on the inside, the microwave source is disposed.

[0033] One of the important aspects of this invention is the manner in which water is used for the washing process. At the frequency of interest used in commercial microwave ovens (2.45 GHz), microwaves have a penetration depth of only 0.5 inches in water [Sutton, Microwave Processing of Ceramic Materials, Amer. Cer. Soc. Bull. Vol. 68, No. 2, pp 376-386, 1989]. Hence, too much water will defeat the washing efficiency available through microwave energy. Consequently, in the apparatus 100 depicted in FIG. 3, the amount of water used during the microwave exposure time, should be just enough to soak the clothes (typically few inches in depth). Laundry items will be circulated in the microwave-transparent rotating drum (identical to the movement in state-of-the-art commercial dryers) and simultaneously be exposed to microwaves. During the time laundry items are out of the water at the bottom of the cavity, microwave energy will penetrate into the water soaked in the fabric. This will heat the water soaked in the fabric, as well as cause the micro-agitation, which will enhance the cleaning process. During the rotation of the drum, when clothes fall in the water at the bottom, they will soak in additional soapy water, as well as release some of the dirt removed during the time of microwave exposure. Thus a combination of mechanical agitation provided by the rotation of the drum 16 and the micro-agitation provided by the microwaves, will result in improved cleaning. Rinsing with sufficient water can be carried out routinely, like the state-of-the-art rinsing process cycles in most washers. For the spinning cycle the speed of rotation of the drum could be selected to be much higher to make use of the centrifugal action to remove most of the water.

[0034] For the final drying, the speed of the rotating drum could be reduced again with the microwave power on and air blown through the laundry items, similar to state-of-the-art dryers. In this case, just cold air (or air circulated through the power supply and electronics) could be blown and the heating of the residual water will be performed with microwave energy. Since microwave energy will be preferentially heating just the moisture, it will rapidly drive it out even from thick fabrics. The moisture will be taken away by the air flowing through the chamber. Thus the two separate steps of washing and drying can be integrated into a single machine.

[0035] The better quality washing using microwaves is illustrated with the following examples.

EXAMPLE 1

[0036] Laundry items having routine dirt were placed in a microwave applicator using regular laundry detergent and water to prove the concept that washing is possible with microwave irradiation. The dirt was removed from the fabric and it appeared brighter than a regular wash.

EXAMPLE 2

[0037] As mentioned above in Example 1, since the fabrics appeared brighter than a regular wash, fabrics previously washed in a regular washing machine (e.g. white socks still having a stain at the heel) were then irradiated with microwave energy in a soap and water mixture for 10 minutes with minimal mechanical agitation. The dirt stains that remained after regular washing were removed with microwave exposure, proving that molecular agitation within the fabric provided by microwaves did the job that mechanical agitation with the regular washing machine could not.

EXAMPLE 3

[0038] Since exposure to microwave energy increases the temperature of the water used to wash an item, it may be suspected that the temperature of the soapy water may be higher in the case of microwave exposure. To clarify this situation, simple heating of the fabric in soapy water was carried out by microwaves as well as by heating on a stove to achieve identical temperatures. There was no agitation in either case. The microwave-washed fabric appeared brighter than the one heated on the conventional stove.

EXAMPLE 4

[0039] Identical stains of engine oil, grease, Pepsi, Kool Aid, ketchup and wood stain (for varnishing), were intentionally put on identical towels. FIG. 4 shows a picture of the two towels showing the identical stains mentioned above. FIG. 5 schematically illustrates and briefly describes the stains. These towels were later washed with an equal amount of detergent and water for 20 minutes each, one by a commercial washer and the other with microwave exposure. The towels were then rinsed and dried. FIG. 6 shows the towels pictured separately. Some of the hard-to-remove stains did not go away in both cases, but the presence and the extent of the stains removed highlights the differences in washing by the two methods. The towel which was washed using microwaves had much lighter stains, as compared to its counterpart that was washed in a conventional washing machine. The purpose of this experiment was not to completely remove the stains, but to have the opportunity to make an distinct comparison, which is apparent from this picture. FIG. 7 shows the towels washed by conventional and microwave techniques, pictured together to eliminate errors in brightness and contrast in photography. The background on the towel (exclusive of the stained regions) washed by microwaves was brighter, as if it had been bleached, when compared to the towel washed by conventional washing machine. The contrast is first visible on the bands (labeled M and C) between the arrows on the photograph. The band labeled M is brighter than the relatively yellowish tinted band labeled C. Once this difference is identified it can be observed on the remainder of the towels. Upon direct viewing, the difference between the whiteness of the two towels pictured in FIG. 7 is immediately obvious; only the microwave-washed towel looks truly white, as if bleached.

[0040] In order to provide more concrete evidence of the improvement in cleaning with the use of microwave energy, microscopic observations were made of the towels washed by microwave and conventional means. Microscopic observation of the stains revealed that grease was still excessively present in the fabric network and within the fibers for the towel washed conventionally. FIG. 8 shows a comparison of the conventional and microwave washing efficiency. Although the grease was not completely removed, washing with microwave energy was much more effective in removing the grease from within the fabric network. This efficient removal resulted in an overall reduction in the stains apparent in FIG. 6. FIG. 9 shows a microscopic picture of the effective cleaning of engine oil with microwave energy, whereas FIG. 10 shows a comparison of the extent of cleaning of oil wood stain by both methods. It is obvious from these figures that microwave energy is able to remove the grease/oil etc. from within the fabric network as well as within the fiber much more effectively than the conventional washing techniques. This internal cleaning between fibers and within the fibers with microwave energy is believed to be responsible for the enhanced cleaning (brightness) and the difference in stain removal between the two methods that is obvious in the macroscopic photographs.

[0041] Although the invention has been described in detail in the foregoing embodiments for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be described by the following claims. 

What is claimed is:
 1. A method for washing items having cloth comprising the steps of: placing the items having cloth into a washing machine; and irradiating the items with microwaves to clean the items.
 2. A method as described in claim 1 including after the placing step, there is a step of agitating mechanically the items in the washing machine.
 3. A method as described in claim 2 including before the agitating step, there is a step of adding liquid to the washing machine so the items are made wet by the liquid.
 4. A method as described in claim 3 including before the agitating step, there is a step of placing detergent into the washing machine so the items are contacted by the detergent.
 5. A method as described in claim 4 wherein the irradiating step includes a step of irradiating the items with microwaves at 2.45 GHz or other frequencies.
 6. A method as described in claim 4 wherein the adding the liquid step includes a step of adding approximately 3 gallons (or less) of water to one cubic feet of uncompressed dry laundry load during the washing cycle.
 7. A method as described in claim 6 including after the irradiating step, there is a step of drying the items with microwave energy.
 8. An apparatus for cleaning items having cloth comprising: a housing having a microwave cavity; a drum disposed within the cavity which is made of a material which is transparent to microwaves, said items are disposed in the drum when they are cleaned; a microwave source in communication with the cavity to provide microwave energy to the cavity; a fluid source in contact with the cavity to provide fluid to the cavity; and a mechanism for moving the drum, said moving mechanism connected to the drum.
 9. An apparatus as described in claim 8 including a mechanism for releasing fluid from the cavity, said releasing mechanism connected with the cavity. 